Apparatus for removing condensate from a sealed face visor and for indicating a dangerous environmental temperature

ABSTRACT

A face mask used by a firefighter and/or miner includes a seal between the mask interior surfaces and skin on the face of a user. A port on the sealed visor receives a hose for supplying a regulated amount of air from a compression air tank carried by the user. A portion of the mask in the form of a visor covering the eyes of the user is transparent to visible optical energy. The mask has a tendency while used to have condensate formed thereon, causing the transparent portion to be fogged. An electrically activated device in the form of a heater and/or fan, on the mask prevents formation of and/or removes the condensate. A battery in a housing carried by the user activates the electrically activated device. The housing includes heat insulation to prevent the battery from being damaged by high temperatures in the vicinity of the user. The power supply for the transparent visor energizes a temperature sensor for enabling a firefighter to be warned that he/she is in an unsafe, excessively hot environment, i.e. a temperature of 125 degrees Fahrenheit or greater.

TECHNICAL FIELD

The present invention relates generally to devices (referred to asself-contained breathing apparatus, SCBA) for firefighters and/or minersand more particularly to such devices that include electricallyactivated means for removing condensate from an optically transparentvisor portion of a face mask of the SCBA.

BACKGROUND ART

SCBA's for firefighters and/or miners include face masks arranged insealed relationship around the facial skin of the firefighter or miner.The miner or firefighter is supplied with gas, typically compressed air,from a bottled source carried on the back of the firefighter or miner.Gas flows from the source to inside the sealed mask via a flexible hoseconnected to an inlet of the sealed mask. The aforementioned equipmentis used because of noxious fumes encountered by firefighter and/orminers working in the environment of fire in a modern building or in amine.

A problem with these sealed face masks is that condensate has a tendencyto form on an optically transparent visor carried on the mask in frontof the user's eyes to enable the user to see the surroundingenvironment. The condensate on the visor obscures (i.e., fogs) thevision of the user, frequently to the point where the firefighter orminer is unable to function adequately in the environment where he islocated.

Condensate forms on the visor interior, i.e., a surface of the visor inclosest proximity to the face of the user, as a result of perspirationfrom the user vaporizing and condensing on the visor interior surface.Condensate forms on the visor exterior when the user enters a region ofvery high humidity and elevated temperature. For example, when afirefighter applies high pressure water to a very hot object,superheated steam is formed and condenses as liquid on the visor.

I have been advised that nose cups have been unsuccessfully used in thepast in an attempt solve the condensate problem. However, prior artdevices have not prevented sealed visors of SCBA's from becomingvirtually opaque as a result of condensate forming thereon. In the past,when firefighters and miners have had their vision obscured as a resultof condensate being formed either on the interior or exterior visorsurface, the only safe remedy has been for the user to leave thepremises. Such a procedure is obviously unsatisfactory because itreduces the amount of time that the firefighter or miner can remain onthe job. In the case of a firefighter it may prevent extinguishing afire in a burning building. In the case of a miner it may prevent rescueof humans trapped in a mine explosion.

It is, accordingly, an object of the present invention to provide anapparatus for removing condensate from a visor of a sealed SCBA facemask.

It is another object of the present invention to provide a structure forremoving condensate from a sealed SCBA transparent face visor whereinthe condensate removing apparatus is electrically activated by a powersupply carried by the user.

Still another object of the invention is to provide a condensateremoving device for a visor of a sealed SCBA face mask, which device isparticularly adapted to be used under many environmental situationsincluding the high temperatures and noxious fumes encountered in firesin modern buildings.

Still another object of the invention is to provide a device forremoving condensate formed on an exterior surface of a visor of a sealedSCBA face mask wherein the condensate results from super heated steambeing generated in response to high pressure water being incident on ahot, burning surface.

Still another object of the invention is to provide an apparatus forremoving condensate formed on an interior surface of a sealed SCBA visorwherein the condensate results from a user perspiring because of hightemperature environmental conditions and the work involved in carryingmodern emergency apparel, e.g., a firefighting suit.

THE INVENTION

According to one aspect of the present invention, condensate is removedfrom and/or prevented on a visor of a face mask of the type adapted tobe used by a firefighter and/or miner. The mask includes a seal betweeninterior surfaces thereof and facial skin of a user and a port forreceiving a hose for supplying a regulated amount of gas from a tank tothe user. A portion of the face mask covering the eyes of a user istransparent to visible optical energy. The mask transparent portion hasa tendency while used by the firefighter or miner to have condensateformed thereon resulting in that portion of the mask becoming fogged orobscured. An electrically activated heater or fan on the mask energizedby a battery in a pack carried by the user heats or draws dry air fromthe gas source across the mask transparent to prevent formation ofand/or remove the condensate from the mask transparent portion.

In the preferred embodiment a battery in a battery pack mounted on aback pack for carrying the gas tank has sufficient energy, when fullycharged, to activate the heater or the fan to remove the condensate fora time interval at least equal to the time a fully loaded tank suppliesgas to the mask and the user via the hose. An electric lead lineconnected between the battery pack and the electric heater or fansupplies current from the battery to the heater and/or fan.

The battery pack preferably contains a rechargeable battery. Suchbatteries are capable of providing the required current only whileoperating at temperatures up to about 110° F.. At temperatures in excessof about 110° F., the batteries have a tendency to fail or to provideexcessive currents resulting in excessively high battery energydrainage. This may prevent the batteries from operating over therequired time interval, i.e., for a length of time in excess of the airsupply time of the tank. To overcome these problems the battery pack hasinsulated walls to enable the battery to remain in proper operatingcondition even though a user, such as a firefighter or a miner, is in anenvironment having a temperature as high as 125° F.

In accordance with a further aspect of the invention, a firefighter iswarned when he is in an excessively hot environment. Firefighters shouldnot remain in burning structures having a temperature in excess of 125°F. If a firefighter stays in such an environment for an extended timeinterval, in excess of one minute, he is likely to sustain physiologicaldamage, even though wearing a modern firefighter's uniform.

It is, accordingly, still a further feature of the invention that thepower supply for the transparent visor energizes a temperature sensorfor enabling a firefighter to be warned that he is in an unsafe,excessively hot environment. The sensor and an aural indicatorresponsive to the sensor are located on a housing for the battery pack.The sensor includes a normally closed bi-metal switch that is opened inresponse to the excessive temperature being encountered. The bi-metalswitch has hysteresis so that it remains open until the sensedtemperature drops appreciably below the level which caused the contactsto open initially. By using normally closed contacts problems of contactdirt are reduced materially. The hysteresis characteristic is importantto prevent false initial alarms and to assure the firefighter receivinga prolonged warning once the excessively high temperature region hasbeen encountered. In the preferred embodiment the bi-metal switch opensat a temperature of 125° F. and stays open until the sensed temperaturedrops to 105° F.

It is, accordingly, still another object of the present invention toprovide a new and improved device for warning a firefighter that he isin an excessively high temperature environment.

An additional object of the invention is to provide a new and improvedelectrically activated device for removing condensate from an opticallytransparent visor of emergency personnel and for warning the emergencypersonnel that he is in an excessively high temperature environment.

The electric heater can be painted on the interior visor surface asdisclosed in my U.S. Pat. No. 4,638,728, or on the exterior visorsurface, or it can be silk screened. If silk screened, silk screeningink is applied through a silk screen mask to a flat cellulose diacetateblank. The ink is then dried, preferably by air jet drying at about 120°F. for about 20 seconds. The Plexiglas sheet is then formed into visorshape and cured by heating in an oven at about 325° F. for about 20minutes on a drape and/or vacuum form. The temperature of the visorduring the drying, as well as bending and curing stages, must becarefully controlled to assure proper application of the ink as well asthe mechanical integrity and transparency of the visor.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an illustration of a firefighter equipped with an SCBAincluding an electrically activated heating device for removing and/orpreventing visor condensate in accordance with one embodiment of thepresent invention;

FIG. 2 is a detailed view of a female connector on a lead and a matingpart of a male connector on the visor as well as a portion of the visorand face mask of the SCBA device illustrated in FIG. 1;

FIG. 3 is a side sectional view of the connector parts illustrated inFIG. 2;

FIG. 4 is a perspective view of a housing for a battery adapted to beutilized with the combination of FIG. 1;

FIG. 5 is a view of the interior of the battery housing illustrated inFIG. 4;

FIG. 6 is an electric circuit diagram including a heater coilillustrated in FIGS. 1 and 2, as well as for detecting excessivetemperature and signaling same;

FIG. 7 is a back view of a second embodiment of a face mask inaccordance with the invention wherein a fan draws air from a gas tankcarried by the user across the visor; and

FIG. 8 is a partial view of another embodiment of a visor wherein thevisor carries a heating coil and fan that are electrically connected inseries with each other.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is now made to FIG. 1 wherein firefighter 11 is illustrated aswearing a conventional metal hard hat 12, fire protection coat 13 andself contained breathing apparatus (SCBA). The SCBA includes a face maskcontaining rubber like shell 10 that is in sealing relation around theperiphery of the face of firefighter 11. On face shield 10 is mountedoptically transparent, visor 14 formed from an organic compound,preferably cellulose diacetate, that is located in front of the eyes andnose of firefighter 11. Visor 14 is secured to face shield 10 by snaps 8to facilitate removal of the visor from the face shield. Strap 7 holdsface shield 10 securely in place on the face of firefighter 11 so theperiphery of the face shield abuts against the facial skin of thefirefighter to form a gas seal for his nose and mouth. Strap 7 isconnected by fastener 6 to opposite exterior portions of face shield 10at the same level as the ear of the firefighter 11. Strap 7 extendsabout the top of the head of the firefighter

Face shield 10 includes aperture or orifice 9 into which hose 15 isfitted in sealing relation. Hose 15 extends to compressed air metal tank16 by way of regulator 17, line 20 and valve 19. Tank 16 is mounted onthe back of firefighter 11 by harness 18. Initially, tank 16 typicallyhas enough compressed air therein to enable firefighter 11 to work forabout 10 to 15 minutes in an environment of noxious fumes as frequentlyexists in fires in modern structures. The foregoing structure iswell-known to those skilled in the art of modern fire fightingtechniques.

A problem with the foregoing, prior art structure is that the interiorand exterior surfaces of visor 14 have a tendency to become fogged,resulting in the vision of firefighter 11 becoming obscured whenattempting to look through transparent visor 14. The interior face ofvisor 14, i.e., the face of the visor closest to the face of firefighter11, becomes fogged as a result of perspiration from the face of thefirefighter vaporizing and condensing on it. The exterior face of visor14 becomes fogged when excessive water vapor, e.g., steam, in the regionwhere firefighter 11 is located. Excessive water vapor occurs in theregion for various reasons, e.g., in response to high pressure waterfrom the firefighter's hose being incident on a hot, burning object. Thesteam from the object condenses on the exterior face of visor 14.

The fogging problem is such that firefighters frequently must leave aburning structure, remove visor 14 and attempt to wipe the visor cleanof the condensed vapor. Such a procedure is disadvantageous because itreduces the number of persons available for fighting the fire.Furthermore, it is dangerous for firefighters in the structure to moveabout the structure with a fogged, vision obscuring visor. While itmight seem that the condensed vapor on the interior surface of visor 14would be removed in response to the compressed air from tank 16 flowingacross the visor on its way toward firefighter 11, it has been found,through actual experience, that this is not the case, probably becauseair flowing through orifice 9 is sucked by the nose and mouth offirefighter 11 and does not flow over the interior surface of visor 14.The problem has also not been solved by deflecting vapor from the noseand/or mouth of the user toward orifice 9 with a nose cup.

In accordance with one embodiment of the present invention, thecondensed vapor on the interior and exterior surfaces of visor 14 isremoved by heating the portion of the visor in front of the eyes offirefighter 11. Heat is applied to the portion of visor 14 in front ofthe eyes of firefighter 11 by supplying electric current to heating coil21, preferably a metal film coated or deposited on the interior surfaceof visor 14. Heating coil 21 is dimensioned so that it has a substantialresistance to electric current and is preferably shaped as pluralhorizontally extending straight lines connected together at the endsthereof by vertically extending straight lines, as disclosed in mypreviously mentioned U.S. patent and as illustrated in FIG. 8.

Heating coil 21 can be deposited on the interior surface of visor 14 bypainting or pad printing a layer of copper covered by a silver layer onthe curved visor interior surface. Alternatively, core 21 is formed byapplying a silver silk screening ink through a silk screening mask to aflat blank sheet formed of an organic compound, preferably cellulosediacetate. The ink on the sheet is then heated with an air jet drier forabout 20 seconds in the range of 120° to 150° F. The flat blank with thedried ink is then curved into shape and cured so the coil is on theinterior surface of visor 14, i.e., the surface having the greatestcurvature. To these ends the flat sheet carrying the dried silkscreening ink is allowed to cool to room temperature and is then placedin an oven on a drape and/or vacuum form so the sheet surface on whichthe silk screened ink is located abuts against a drape form and/or aform having apertures through which a vacuum is drawn. The flat sheet isinserted into the oven while the sheet and oven are at room temperature.The oven thermostat is then raised to 325° F., causing the oventemperature to rise quickly to 325° F. The sheet stays in the 325° F.oven for 20 minutes and then removed from the hot oven. In the oven thesheet is curved to the desired shape while being cured.

It has been found that these parameters are important and for someparameters essential in obtaining a visor having the desired shape andtransparency, in combination with a silk screened heating coil 21. Theyare also important or essential for continuity (thickness and width) ofsilk screened coil 21 to achieve the necessary resistance and continuityalong the length of the coil for proper heating of the visor. If thetemperature of the flat blank sheet during the drying operation is lessthan 120° F. the ink drying time is excessive for a commercialmanufacturing process. If the blank is at a temperature greater than150° F. and the drying duration exceeds 20 seconds the amount of heatapplied to the sheet causes the organic material thereof to set,resulting in distorted visual properties of the visor after the curingoperation. If the curing temperature is appreciably less than 325° F. orcuring is for less than about 20 minutes the sheet cannot be bent intoshape. If the curing temperature appreciably exceeds 325° F. or curingis for more than about 20 minutes, excessive heat is applied to visor 14causing the silk screening ink to run on the visor or form to adverselyaffect electrical properties of coil 21 and reduce the transparencyand/or structural integrity.

By bending the blank so the silk screening ink is on the interiorsurface of visor 14, i.e., the surface having the greater curvature andan area slightly less than that of the flat blank, the silk screeningink is compressed on itself to more positively assure continuity of coil21. Applying the silk screening ink to the surface of the blank thatbecomes the visor exterior surface, i.e., the surface of visor 14 havingthe lower curvature, has been experimentally found to cause adverseeffects because the ink has a tendency to break as the area of the inkbearing surface increases during forming. If the silk screening processis employed it is important that the steps be performed as stated toprovide proper adherence and geometry, including continuity of the driedsilk screening ink and to preserve the structural integrity andtransparency of visor 14.

It has also been found that the high resistivity of silk screened coil21 causes hot spots of the corners of the coil where the horizontal andvertical stripes intersect, if the corners are square. Further hot spotsdevelop at the intersections of connector with silk screened coil 21.The reduced thickness of the silk screened layer relative to thethickness of the painted or pad printed layers causes the silk screenedcoil to be more resistive than the other types of layers, resulting inthe hot spots which can cause the melting of visor 14. To overcome thishot spot problem, silk screened coil 21 is preferably rounded at thecorners thereof where the horizontal and vertical stripes intersect asillustrated in FIGS. 1, 2 and 8. Further, the width of the coil isincreased in the region where the coil engages and is in close proximityto connector 25, as illustrated in FIG. 2. In all other regions, coil 21has uniform width and thickness dimensions.

Electric current is supplied to heating coil 21 from a battery packincluding rechargeable battery 22 that is carried in metal housing 23,shaped as a right parallelepiped. Battery 22 is preferably a 12 volt,1.5 ampere hour rechargeable gel cell, as available from Globe BatteryDivision of Johnson Controls, Inc. The gel cell type battery isadvantageous because it can withstand the intense heat to which it maybe exposed, without exploding. A rechargeable lead battery is verylikely to explode in the firefighting application.

Current from battery 22 is supplied to heating coil 21 by way of helicalcoaxial electrical cable 24, fixedly mounted on gas line 20 betweenregulator 17 and adjustable valve 19, carried by tank 16. Cable 24extends along line 20 until just before the line is connected toregulator 17, where the cable leaves line 20 and extends freely toconnector 25 on visor 14. Cable 24 is helical and hose 15 is corrugatedso they do not impede the movement of firefighter 11.

As illustrated in FIGS. 4 and 5, housing 23 for battery 22 is fixedlymounted on metal strap 31 that extends about and is fixedly secured totank 16 by clip 32. Metal strap 31 is secured to tank 16 to enable thetank to be carried by harness 18 that goes over the shoulders offirefighter 11, as well known to those familiar with SCBA. To preventdamage to rechargeable battery 22 due to excessive ambient heat, whichcan cause the battery to discharge at an excessively high rate, all sixinterior walls of housing 23 are lined with thermal, dielectricinsulating pads 34, preferably constructed of STYROFOAM. Pads 34 haveexterior faces bonded to corresponding interior faces of housing 23. Thecorresponding exterior faces of pads 34 and the interior faces ofhousing 23 have the same shape and about the same exterior dimensions.

Clip 32 is fixedly mounted on housing 23 so that relatively short,transverse housing wall 33 is generally horizontal. On wall 33 arefixedly mounted female coaxial electric connector 134, green lightemitting diode 35, red light emitting diode 135 and on-off pivotingswitch 36. Electric leads of connector 134, diodes 35 and 135, as wellas switch 36, extend through apertures in wall 33 and are connectedtogether on the inside face of wall 33 and to leads 37 from battery 22,which extend through small openings in the pad 34 abutting against wall33. Connector 134 receives male coaxial connector 61 at one end of thecable or a male connector of a battery charger. (To show the physicalarrangement of the leads connecting connector 134, lamp 35 and switch 36and leads 37, the pad 34 abutting against wall 33 is illustrated in FIG.5 as being partially broken away.)

To provide access to battery 22 and enable the battery to be removed forreplacement purposes, wall 38 of housing 23 is connected by hinge 39 towall 41 of the container and by screws 42 which engage threaded bores 43in wall 44. To provide a tight, waterproof seal between top wall 38 andthe remaining walls of container 23, rubberized gasket 45 extendsupwardly from the sidewalls of container 23 for engagement with theperipheral portion of the inside face of top wall 38.

Battery housing 23 also carries an electric circuit, FIG. 6, fordetecting excessively high temperatures, dangerous to firefighter 11,and for providing the firefighter with an aural warning of suchexcessive temperature. The circuit is powered by battery 22 while switch36 is pivoted to the closed state. To these ends, mounted on theexterior of wall 33 is sealed temperature detector 51, including amembrane 52 behind which is located bi-metal contacts 53; the membraneenables contacts 53 to be at about the same temperature as theenvironment where firefighter 11 is located. Bi-metal contacts 53 arenormally closed because such an arrangement is more reliable thannormally opened contacts in the presence of a dirty environment asencountered in burning structures and mines. Contacts 53 have ahysteresis or dead band characteristic so that they are closed fortemperatures rising from room temperature or below to 125° F. At 125°F., contacts 53 open circuit and remain open circuited until thetemperature to which they are exposed drops to less than 105° F., atwhich temperature the contacts again close.

While contacts 53 are open, oscillator circuit 54 mounted on theinterior face of wall 33, is activated to supply a pulsed audiofrequency carrier signal to piezoelectric crystal 55, mounted on topwall 38 of housing 23. Typically, the pulses occur about once every 10seconds, have a duty cycle of about 10% and a carrier frequency of about1 kHz.

Crystal 55 is positioned on wall 38 behind metal grill screen 56, whichfills an opening on wall 38. When oscillator 54 is activated in responseto contacts 53 being open circuited, the oscillator supplies a periodicelectric pulsed audio frequency signal to crystal 55. Crystal 55converts or transduces the electric signal supplied to it by oscillator54 into an acoustic or aural signal having sufficient intensity to beheard by firefighter 11. Thereby, firefighter 11 is provided with anaural warning that he should leave the burning structure because it isexcessively hot and may cause him damage. The aural signal can also beused to advise the presence of a disabled firefighter.

When switch 36 is activated to the on position and male connector 61 atthe end of cable 24 is connected into female connector 134 on housing23, current is supplied by battery 22 via cable 24 to heating coil 21.The connection from cable 24 to heating coil 21 is via connector 25,fixedly mounted on visor 14 so that it is electrically connected toopposite terminals of coil 21, as disclosed in my aforementioned patent.Connector 25, however, is modified so that one end of cable 24 can beselectively inserted into and removed from the connector. Thearrangement is such that cable 24 is not pulled from connector 25 as aresult of the free portion of the cable, between line 20 and connector25, having debris fall on it. Cable 24 can be removed from connector 25only by simultaneous pushing and twisting of the end of the cable whichfits into connector 25, operations easily performed by firefighter 11when he wants to remove face shield 10 or visor 14 from face shield 10.

To these ends, as illustrated in FIGS. 2 and 3 at the end of cable 24which is inserted into connector 25 is connector 60 including metalsleeve 61, electrically connected to a coaxial shielded lead (not shown)of cable 24. Sleeve 61 includes a pair of diametrically opposed slots62, each having a longitudinally extending segment 63, an arcuatelyextending segment 64 and an ear 65 which extends from segment 64 towardthe top edge of sleeve 61 where longitudinal slotted segment 63 begins.Slot 62 engages radially extending metal pin 66 on dielectric stub shaft67 of connector 25; shaft 67 extends downwardly from the remainder ofconnector 25. Pins 66 are connected via connector 25 to one terminal ofheating coil 21 via lead wire 73 in connector 25. The remaining terminalof heating coil 21 is connected via lead wire 74, contact 75 and metalcompression spring 76 in connector 25 to longitudinally extending metalpin 68, mounted in and coaxial with stub shaft 67. Compression spring 76biases pin 68 inside of stub shaft 67 so that pin 68 normally extendsbeyond the end of the stub shaft by a distance equal to the distancebetween the top edge of sleeve 61 and the intersection of the sleevewith dielectric case 70 from which the sleeve extends. Centrally locatedin cavity 71 of case 70 is contact 69 that is electrically connected tothe center conductor of cable 24 and electrically insulate from sleeve61.

In operation, connector 60 is inserted on connector 25 by placing sleeve61, having a diameter slightly in excess of the diameter of stub shaft67, about the stub shaft so that slot portions 63 are aligned with pins66. Connector 60 is then pushed into stub shaft 67 until pins 66 are inproximity to the bottom of slot portion 63, i.e., the portions of slot62 farthest away from the top edge of sleeve 61. Pin 68 now engagescontact 69 and the pin is in the fully retracted position. Connector 60is then turned so that slot portions 64 turn about pins 66 until thepins 62 are aligned with ears 65, at which time connector 60 isreleased. The spring bias exerted against pin 68, thence against contact69, causes pins 66 to seat against the edges of ears 65 closest to thetop edge of sleeve 61. Thereby, longitudinally extending pin 68 is urgedby the compression spring against contact 69 to establish positiveelectrical and mechanical contact between pins 66 and 68 and the shieldand the interior lead of cable 24.

FIG. 6 is an electric circuit diagram of the electrical componentsincluded in housing 23 and connected to heating coil 21. Battery 22 isconnected to the remainder of the circuit through fuse 81, mounted onthe interior face of wall 33. Fuse 81 is connected to switch 36 which,when activated into the "on" position, causes current to flow frombattery 22 through lamp 35 to energize the lamp. When cable 24 isconnected to connectors 25 and 134, current flows from battery 22 to,fuse 81, switch 36 and cable 24 to heating coil 21.

Connected in shunt with lamp 35 is series resistor 83 and a first branchincluding the series combination of resistor 82 and normally closedbi-metal contacts 53, as well as a second branch, in parallel with thefirst branch; the second branch includes power supply terminals 84 ofoscillator 54. Resistors 83 and 82 have a sufficiently large value toprevent excessive current drain from battery 22 while contacts 22 areclosed. In response to temperature sensing contacts 53 being in thenormally closed state, oscillator 54 is de-energized because the voltageacross terminals 84 is insufficient to power oscillator 54. In responseto contact 53 being open-circuited because of excessive temperaturebeing detected, the voltage across terminals 84 increases, causingoscillator 54 to become activated to supply a pulsed carrier signal topiezoelectric crystal 55.

Green light emitting diode (LED) 235 and red LED 135 are connected incircuit with battery 22 to signal to the firefighter whether battery 22has sufficient energy to defog mask 14 for a sufficient time to warrantinsertion of a new air tank 16. For air tanks having a 20 minutecapability, as is typically employed, the voltage of battery 22 mustexceed 8.5 volts for the type of battery previously mentioned. If thevoltage of battery 22 is greater than 8.5 volts, associated with thebattery having sufficient energy to power coil 21 for more than 20minutes with enough current to prevent fogging of mask 14, green LED 235is energized. If the voltage of battery 22 is less than 8.5 volts,associated with the battery having insufficient energy to power coil 21for more than 20. minutes with enough current to prevent fogging of mask14, red LED is energized.

To these ends, LEDs 235 and 135 are connected in separate branchcircuits to battery 22 via series resistor 136. The branch circuitincluding LED 235 includes resistor 137, connected in series with theLED. One terminal of resistor 138 is connected to a common terminal ofresistors 136 and 137; the other terminal of resistor 138 is connectedto parallel branch circuits 139 and 140, respectively including zenerdiode 142 and LED 135. Circuits 139 and 140 respectively include currentlimiting resistors 143 and 144. The characteristics of diodes 235, 135and 142 and the values of diodes 136-138, 143 and 144 are selected forthe type of battery 22 and the characteristics of coil 21 such thatdiode 235 is energized in response to the voltage of battery exceeding8.5 volts. For voltages of battery 22 above 8.5 volts, zener diode 142is activated to a conducting state causing the voltage across and/or thecurrent through diode 135 to be low enough to prevent activation of LED135. The values of diodes 136-138 are such that the low impedance ofdiode 142 does not affect energization of diode 235. For voltages ofbattery 22 less than 8.5 volts, LED 235 is de-energized and zener diode142 is switched to a nonconducting state. The voltage applied to red LED135 is then sufficient to activate the red LED. The firefighter isthereby provided with a convenient indication as to whether or notbattery 22 must be replaced or recharged at the time a new air bottle isput into service.

A supplemental or alternative structure for removing condensate from theinterior surface of visor 14 is to fixedly position fan 91 on theinterior surface of the visor just below the top edge of the visor halfway between the opposite side edges of the visor as illustrated in FIG.7. Low voltage DC motor 92 of fan 91 is electrically connected to beenergized by battery 22 via cable 24 and the terminals on visor 14 bylow resistance leads 93 formed on the visor interior surface in a mannersimilar to that described for coil 21. Leads 93 extend about theperiphery of visor 21 so they do not obstruct the vision of thefirefighter and have a considerably greater thickness and width, buttotal shorter length than coil 21 so that almost the full voltage ofbattery 21 is delivered to motor 92 with minimum current dissipation.Alternatively, motor 92 has a very low voltage rating and the armaturecoil thereof is connected in series with coil 21 by a pair of leads 95deposited on visor 14 and connected via wires 96 to upper most lead 97of coil 21, as illustrated in FIG. 8.

Blades 94 of fan 91 suck dry air from tank 16 flowing through orifice 9across the interior surface of visor 14 prior to the air being inhaledby firefighter 11 to remove the condensate from the visor interiorsurface and provide a curtain of dry air that tends to prevent the flowof vapor from the face of the firefighter to the visor interior surface.After the air flowing through orifice 9 that has been drawn upwardlyacross visor 14 by blades 94 has passed through the blades it is inhaledby firefighter 11.

While there have been described and illustrated several specificembodiments of the invention, it will be clear that variations in thedetails of the embodiments specifically illustrated and described may bemade without departing from the true spirit and scope of the inventionas defined in the appended claims.

We claim:
 1. In combination, an assembly including a gas tank of thetype adapted to be worn on the back of a firefighter or miner and meansmounted on the tank for securing the tank to the back of a user, a facemask for the user adapted to be mounted in sealed relation with the faceof the user to cover the eyes, mouth and nose of the user, a portion ofthe face mask covering the eyes of the user being transparent to enablethe user to see through said portion, hose means connected between thetank and the face mask for supplying a regulated amount of gas from thetank to the face mask so that gas from the tank flows through the hoseto the nose of the user, said portion of the face mask having a tendencywhile used by a firefighter or miner to have condensate formed thereonresulting in said portion of the mask becoming fogged and causing visionof the user through the face mask to become obscured, and electricallyactivated means on the face mask for preventing and/or removing thecondensate from the face mask in said portion of the mask; thecondensate preventing and/or removing means including: a battery packmounted on the assembly, electric heater means mounted on the face maskfor applying sufficient heat to said portion of the mask in response tocurrent from said battery pack mounted on the assembly, said batterypack having sufficient energy when fully charged to heat the face maskportion to prevent and/or remove the condensate for a time interval atleast equal to the time a fully loaded tank supplies gas to the mask andthe user via the hose, and electrical conductor means connected betweenthe battery pack and the electric heater means for supplying sufficientcurrent from the battery pack to the heater means to heat said portionof the mask sufficiently to remove the condensate, the condensatepreventing and/ore removing means including electrically activated meanson the face mask for sucking gas flowing through the hose means acrossthe transparent portion prior to said gas flowing to the face of theuser.
 2. The combination f claim 1 wherein said means for suckingincludes a fan having blades, said transparent portion being positionedbetween an inlet in the face mask for the gas and the fan blades, theinlet being positioned below the transparent portion and the fan bladesbeing positioned above the transparent portion.
 3. The combination ofclaim 2 wherein the fan includes a motor coil connected in seriescircuit with the heater means.
 4. In combination, an assembly includinga gas tank of the type adapted to be worn on the back of a firefighteror miner and means mounted on the tank for securing the tank to the backof a user, a face mask for the user adapted to be mounted in sealedrelation with the face of the user to cover the eyes, mouth and nose ofthe user, a portion of the face mask covering the eyes of the user beingtransparent to enable the user to see through said portion, hose meansconnected between the tank and the face mask for supplying a regulatedamount of gas from the tank to the face mask so that gas from the tankflows through the hose to the nose of the user, said portion of the facemask having a tendency while used by a firefighter or miner to havecondensate formed thereon resulting in said portion of the mask becomingfogged and causing vision of the user through the face mask to becomeobscured, and electrically activated means on the face mask forpreventing and/or removing the condensate from the face mask in saidportion of the mask; the condensate preventing and/or removing meansincluding: a battery pack mounted on the assembly, electric heater meansmounted on the face mask for applying sufficient heat to said portion ofthe mask in response to current from said battery pack mounted on theassembly, said battery pack having sufficient energy when fully chargedto heat the face mask portion to prevent and/or remove the condensatefor a time interval at least equal to the time a fully loaded tanksupplies gas to the mask and the user via the hose, and electricalconductor means connected between the battery pack and the electricheater means for supplying sufficient current from the battery pack tothe heater means to heat said portion of the mask sufficiently to removethe condensate, a temperature sensor powered by a battery of the batterypack, an indicator responsive to the sensor powered by the battery, thetemperature sensor activating the indicator so the indicator signals theuser that he is in an excessively high temperature environment, thesensor including a pair of normally closed bi-metal contacts which areactivated into an open circuited condition in response to theenvironmental temperature exceeding about 125° F. and which return tothe closed condition in response to the environmental temperaturedropping below about 105° F.
 5. The combination of claim 4 wherein thecontacts, indicator and a circuit connected between them are mounted ona housing for the battery.
 6. In combination, an assembly including agas tank of the type adapted to be worn on the back of a firefighter orminer and means mounted on the tank for securing the tank to the back ofa user, a face mask for the user adapted to be mounted in sealedrelation with the face of the user to cover the eyes, mouth and nose ofthe user, a portion of the face mask covering the eyes of the user beingtransparent to enable the user to see through said portion, hose meansconnected between the tank and the face mask for supplying a regulatedamount of gas from the tank to the face mask so that gas from the tankflows through the hose to the nose of the suer, said portion of the facemask having a tendency while used by a firefighter or miner to havecondensate formed thereon resulting in said portion of the mask becomingfogged and causing vision of the user through the face mask to becomeobscured, and electrically activated means on the face mask forpreventing and/or removing the condensate from the face mask in saidportion of the mask; the condensate preventing and/or removing meansincluding: a battery pack mounted on the assembly, electric heater meansmounted on the face mask for applying sufficient heat to said portion ofthe mask in response to current from said battery pack mounted on theassembly, said battery pack having sufficient energy when fully chargedto heat the face mask portion to prevent and/or remove the condensatefor a time interval at least equal to the time a fully loaded tanksupplies gas to the mask and the user via the hose, and electricalconductor means connected between the battery pack and the electricheater means for supplying sufficient current from the battery pack tothe heater means to heat said portion of the mask sufficiently to removethe condensate, and voltage responsive indicator means connected in acircuit with a battery of said battery pack, the circuit and indicatormeans being responsive to the battery voltage and being arranged so thata first type of indication is derived from the indicator means inresponse to the battery having sufficient energy to power the heatermeans for a time in excess of the time that one tank will supply enoughgas to sustain the firefighter or miner and a second type of indicationis derived from the indicator means in response to the battery havinginsufficient energy to power the heater means for a time in excess ofthe time that one tank will supply enough gas to sustain the firefighteror miner.
 7. In combination, an assembly including a gas tank of thetype adapted to be worn on the back of a firefighter or miner and meansmounted on the tank for securing the tank to the back of a user, a facemask for the user adapted to be mounted in sealed relation with the faceof the user to cover the eyes, mouth and nose of the user, a portion ofthe face mask covering the eyes of the user being transparent to enablethe user to see through said portion, hose means connected between thetank and the face mask for supplying a regulated amount of gas from thetank to the face mask so that gas from the tank flows through the hoseto the nose of the user, said portion of the face mask having a tendencywhile used by a firefighter or miner to have condensate formed thereonresulting in said portion of the mask becoming fogged and causing visionof the user through the face mask to become obscured, and electricallyactivated means on the face mask for preventing and/or removing thecondensate from the face mask in said portion of the mask; thecondensate preventing and/or removing means including electricallyactivated means no the face mask for sucking gas flowing through thehose means across the transparent portion prior to said gas flowing tothe face of the user.
 8. The combination of claim 7 wherein said suckingmeans includes a fan having blades, said transparent portion beingpositioned between an inlet in the face mask for the gas and the fanblades, the inlet being positioned below the transparent portion and thefan blades being positioned above the transparent portion.
 9. Incombination, a face mask of the type adapted to be used by a firefighterand/or miner, said face mask including a seal between interior surfacesof the mask and around the mouth, nose and eyes on the face of the userand a port for receiving a hose for supplying a regulated amount of gasfrom a tank to the mouth and nose of a user of the face mask, a portionof the face mask covering the eyes of a user being transparent tovisible optical energy, said portion of the mask having a tendency whileused by a firefighter or miner to have condensate formed thereonresulting in said portion of the mask becoming obscured, andelectrically activated means on the mask for preventing and/or removingthe condensate from said portion, the condensate preventing and/orremoving means including electrically activated means on the face maskfor sucking gas flowing through the hose means across the transparentportion prior to said gas flowing to the face of the user.
 10. Thecombination of claim 9 wherein the condensate preventing and/or removingmeans includes: electric heater means mounted on the face mask forapplying sufficient heat to said portion of the mask in response tocurrent from a battery pack.
 11. The combination of claim 9 wherein saidfor sucking means includes a an having blades, said transparent portionbeing positioned between an inlet in the face mask for the gas and thefan blades, the orifice being positioned below the transparent portionand the fan blades being positioned above the transparent portion. 12.In combination, an assembly including a gas tank of the type adapted tobe worn on the back of a firefighter or miner and means mounted on thetank for securing the tank to the back of a user, a face mask for theuser adapted to be mounted in sealed relation with the face of the userto cover the eyes, mouth and nose of the user, a portion of the facemask covering the eyes of the user being transparent to enable the userto see through said portion, hose means connected between the tank andthe face mask for supplying a regulated amount of gas from the tank tothe face mask so that gas from the tank flows through the hose to thenose of the user, said portion of the face mask having a tendency whileused by a firefighter or miner to have condensate formed thereonresulting in said portion of the mask becoming fogged and causing visionof the user through the face mask to become obscured, and electricallyactivated means on the face mask for preventing and/or removing thecondensate from the face mask in said portion of the mark; the assemblyincluding a temperature sensor for environmental conditions, and anindicator connected to the temperature sensor for signalling the userthat the environmental temperature is excessively high, the indicatorbeing activated in response to the sensed environmental temperatureexceeding about 125° F. and being deactivated in response to the sensedenvironmental temperature dropping below about 105° F.
 13. Thecombination of claim 12 wherein the sensor includes a pair of normallyclosed bi-metal contacts which are activated into an open circuitedcondition in response to the environmental temperature exceeding about125° F. and which return to the closed condition in response to theenvironmental temperature dropping below about 105° F.